Metallic containers, for example, metallic cans, have various shapes and can be classified into three-piece cans and two-piece cans. The three-piece can is called a tinplate-soldered can which has a structure in which a cylindrical can body, a top or cover, and an end are double seamed and sealed. The two-piece can is called a tinplate-pressed can which has a structure in which a can body and an end portion (container body) are formed integrally and a cover is double seamed around the rim of the integral container body to seal the same.
These metallic cans are used as food packaging containers for packaging various foods, juices, soft drinks, dry foods and the like are thus rigid containers of particular excellence in sealing and preservation properties. However, metallic cans have the following points to be improved.
(1) There is a limitation to making the weight light because of the nature of the metallic can;
(2) There is no self-restorative capability if the can is once crushed under an impact and the can is deformed;
(3) High energy cost is required for manufacturing the metallic can in comparison with a plastic container;
(4) The display effect of the outer appearance of the container cannot be freely changed in case the container is made of a metallic material and the display is only carried out by printing operation; and
(5) It is impossible to manufacture a transparent container the contents of which can be verified without opening the container.
For solving these problems or drawbacks of the conventional metallic cans described hereinabove, a container with a metallic cover in which a metallic cover is secured to a plastic container body has been conceived.
In a case where a metallic cover is secured to the plastic container body, the peripheral edge portion of the metallic cover is seamed to a flanged portion of the container body.
As described above, the container with the metallic cover is constructed by seaming the metallic cover to the flange of the plastic container body.
In addition, it is required for the plastic container body to have a precision strength against the flange seaming force, a gas-barrier property capable of improving a content reserving function and an adequate strength of a shell portion thereof.
However, there has not been proposed any container provided with a metallic cover sufficiently attaining or achieving the above described functions, and technology for the manufacturing method and apparatus for such container have been not yet established.